Process for the preparation of heteropoly acid complex compounds of metaphosphoric metasilic acid, metaphosphoric acid and phosphorous pentoxide

ABSTRACT

A process for the production and recovery of oxygen containing compounds of phosphorous or silicon from starting materials comprising orthophosphoric acid and amorphous silica or its hydrates by adding siliceous material to an aqueous solution of orthophosphoric acid and thereafter heating the resulting product to dissolve the added silica and then to effect volatilization and boiling off of at least some of the water of solution and combined water of hydration of said product and continuing the heating to obtain a dry solid product which is at least one oxygen containing compound of phosphorous and/or silicon.

Stats Wilson tet [ 51 Mar. 28, 1972 [7 2] Inventor: Harold W. Wilson, ElPaso, Tex.

[73] Assignee: Wilson Laboratories, line.

[22] Filed: Feb. 18, 1969 21 Appl. No.: 800,292

[52] US. Cl ..252/1l94, 23/165, 23/223, 252/437, 252/449 [51] Int. Cl.301d 17/00, C091: 3/00 [58] Field oi Search ..252/194, 437, 449; 23/165,23/ 182, 223

[56] Relierences Cited UNlTED STATES PATENTS 2,967,153 1/1961 Houston V3,264,086 8/1966 l-lollingsworth etal ..23/165 Primary Examiner-RichardD. Levering Assistant Examiner-Irwin Gluck Att0rney--Clarence A. O'Brienand Harvey B. Jacobson ABSTRACT A process for the production andrecovery of oxygen containing compounds of phosphorous or silicon fromstarting materials comprising orthophosphoric acid and amorphous silicaor its hydrates by adding siliceous material to an aqueous solution oforthophosphoric acid and thereafter heating the resulting product todissolve the added silica and then to effect volatilizationand boilingoff of at least some of the water of solution and combined water ofhydration of said product and continuing the heating to obtain a drysolid product which is at least one oxygen containing compound ofphosphorous and/or silicon.

24 Claims, No Drawin PROCESS FOR THE PREPARATRON OF HETEROPOLY ACllDCOMPLEX COMPOUNDS F METAPHOSPHORIC METASILIC ACID, METAPHOSPHORIC AllDAND PHOSPIHOROUS PENTOXIDE This invention relates to dry granularproducts useful as desiccants and as source materials for thepreparation of phosphorus-oxygen compounds, including P 0 andmetaphosphoric acid and as novel compositions comprised of oxygen,silicon and phosphorus, and to the preparation of such products. Moreparticularly, the present invention relates to the novel productsrecoverable by controlled heating to effect the elimination of waterfrom aqueous solutions of orthophosphoric acid to which either amorphoussilica or its hydrates, i.e., metasilicic acid, disilicic acidororthosilicic acid, have been added.

One object of the invention is to provide a process whereby any aqueoussolutions of orthophosphoric acid regardless of their contents oftrihydrogen phosphate (H PO can be converted into one or many kinds ofseveral new compositions of matter free of water and existing in theform of granular and/or powdery solids.

Another object of the invention is to provide a process for preparingnew compositions of matter which are capable of maintaining suchextremely high rates of water pickup that their percent weight gain frompickup of water per time unit exceeds by more than twice the waterpickup under the same conditions of granular phosphorus pentoxide (99+%P 0 one of the most efficient desiccants known.

Still another object of the invention is to recover metaphosphoricacid(HPO and/or phosphorus pentoxide (P 0 directly from aqueoussolutions of orthophosphoric acid without first reducing the phosphoruscontent of such acid to elemental form followed by burning the elementalphosphorus in excess oxygen as is presently practiced.

A further object of the invention is to provide a process for themanufacture of new compositions of matter containing equivalent P 0 inamounts up to and greater than 80 percent of the weights of suchproducts which have such equivalent P 0 present either in the form ofmetaphosphoric acid (H- PO as metaphosphoric acid (l-lPO and phosphoruspen toxide (P 0 in combination, or as phosphorus pentoxide (P 0 Suchproducts can be prepared so as to contain predetermined quantities ofequivalent P 0 as may be desired ranging in amount from traces up tomore than 80 percent of the weights ofsuch products.

Another object of the invention is to provide a process for theproduction of new compositions of matter whose molecules contain one (1)single strongly ionizable hydrogen ion per each phosphorus atom presentin its structure and no content of weakly ionizable hydrogen ionswhatsoever with such compositions of matter existing as dry, granular,solid substances capable of displaying strong acidic propertiesespecially when brought into contact with either inorganic or organicbases.

Still a further object of the invention is to provide for the productionof heteropoly complex acid compounds containing metasilicic acid and itspolymers and metaphosphoric acid where a molecular ratio of silicondioxide (SiO to phosphorus pentoxide (P 0 can be varied between 4 molsSiO, mol P 0 to 1 mol SiO, 4+ mols P 0 and further, for the productionof compounds containing metasilicic acid, metaphosphoric acid, andphosphorus pentoxide, all in combination and for the production ofcompounds containing silicon dioxide in combination in equal ratio suchas SiO :P O represented by the compound, silicon pyrophosphate, SiPgO1which after preparation can be heat decomposed to liberate sublimed P 0and a residue of nonvolatile crystalline silicon dioxide (SiO,) withoutresorting to the use of white heat temperatures (l,260 C. and above) toeffect such decomposition and liberation of sublimed P 0 as isconventionally required.

These and other objects in addition to those noted above will becomeapparent in the disclosure of this invention which follows.

Essentially, and briefly stated, the process of this invention comprisesheating aqueous solutions of orthophosphoric acid to which have beenadded either amorphous silica (SiO or its hydrates: metasilicic acid,disilicic acid, and orthosilicic acid to bring about the following:

1. Dissolution of the added siliceous material followed byvolatilization and boiling off of the uncombined water of solution andthe combined water of hydration of the orthophosphoric acid, therebyproducing solid heteropoly complex acid compounds of the nature ofH,sio,-x H P0 this being accomplished by heating at temperatures below300 C.;

2. Efi'ecting condensation and partial dehydration of the metaphosphoricacid component of the H siO X HPO so produced by further heating attemperatures between 300 and 575 C. thereby further volatilizing thewater of constitution of the metaphosphoric acid, to form solidheteropoly acid complexes with P 0 adducts of the nature of H SiO -X P 0hpo 3. Decomposing the complexes of 2." above to release volatilemetaphosphoric acid per se and leave a nonvolatile residue of solidsilicon pyrophosphate, SiP O by further heating at temperatures between575 and 800 C.;

4. Effecting decomposition of the silicon pyrophosphate of "3." above tofrom a sublimate of P 0 and leave a residue of nonvolatile crystallinesilicon dioxide by further heating at temperatures between 800 and 1,000C. The values for X and Y of the complex compounds noted above aredirectly related to and dependent upon the quantities of orthophosphoricacid (H;,PO,) present in the aqueous solutions of orthophosphoric acidemployed in the process.

The following chemical equations are considered to be illustrative ofthe reactions taking place in the above described process:

1. SiO; (GHaPO X H 0) H SiO amoraq. orthophosphoric orthophous acidslllclc stllca acid 1a. H sios (GHQ? 04 X H10) H4810. GH P 04 J (X-UHzO(X is equivalent to l to 50 mol wgts. H10 per mol Hi? 04) heat 1HzSiOz-GHPO! 7111 0-300 C. SOT-572 F.

HzSlOr-GHP 0:

heat

4. HzSiOrQPgOs-ZHP 03 T 5. Slog-P205 Slot Pros- At least partialpolymerization of the metasilicic acid occurs in some of the abovereactions causing the formation of disilicic acid, H Si,O for example.However no evidence was found that the metaphosphoric acid polymerizedto the di-, trietc., forms as would be indicated by (HPO representationbut rather the metaphosphoric acid remains present in monomer formrepresented by nHPO While not wishing to be bound by any specific theoryit is believed that the affinity for water exhibited by metasilicic acidand polymers of silicic acid is so much greater than the af finity forwater exhibited by metaphosphoric acid that when mixtures of silicic andmetaphosphoric acids are heated, the water of constitution of themetaphosphoric acid is liberated with increase of temperature and inturntaken up by the metasilicic acid in its attempt to form orthosilicicacid which in turn brings about the formation of silicic acid polymercomplexes and the liberation of the water as steam, as in theequadisllicic acid complex In the above described process, regardless ofthe products to be made, the rate of heating is not critical andoperation at the specified temperatures results in the production ofrelatively uniform products. It is to be understood that localizedoverheating is to be avoided to prevent portions of any product frombeing exposed to temperatures above those desired for the reaction beingeffected. It is preferable to keep the heating temperature of theparticular products themselves under preparation at somewhat lowertemperatures (2550 lower) than the maximum of the temperature rangegiven for the specific product being prepared. Temperatures in theinitial product preparation can be in excess of 300 C. in the earlystages of preparation before the temperature of the products themselveswill approach or reach the maximum of the cited temperatures.

Use of stoichiometric quantities of silica (SiO and orthophosphoric acid(H PO in the process results in very definite products both as to theirqualities and their quantities. For example, it was desired to produce100 grams of a product for use as a desiccant. The product was tocontain approximately 60 grams of equivalent P O and to have acomposition defined by the empirical formula, H SiO -2HPO and to be of acomposition as follows: 25.2% SiO 8.6% H 0, and 67.2% HPO The productwas made by heating a mixture of 110 grams of aqueous orthophosphoricacid solution of 75% H 1 0, content and 26.5 grams of diatomaceoussilica known to contain 95.5% SiO until the temperature of the resultantproduct itself reached 275 C. after which it was cooled and weighed. Thefinished product weighed 100.7 grams. Chemi-' cal analysis of theproduct showed it to contain 59.52% equivalent P and to be composed of24.92% SiO 8.01% H 0, and 67.07% HPO grams of the above product wasaccurately weighed into a flat bottomed dish and the dish with contentswas placed in a desiccator containing a second dish holding 75 ml. of anaqueous solution of sulfuric acid (39% H 80 The dish with product wasremoved periodically from the desiccator during a 100 hour exposureperiod to the aqueous sulfuric acid solution in order to determine itsweight gain caused by removal of water from the aqueous sulfuric acidsolution by the prepared desiccant. Water removal by the productprepared as noted above in comparison with water removal by the samemethod of test by the best known grade of commercially availablegranulated P 0 (99.0+% P 0 is shown in the following tabulated results:

Time Process Product Commercial Product (granular 59.52% (granu1ar99.0+%2 5) 2 5) Wgt. Gain in 5 hrs. 4.2% 2.3%

% Wgt. Gain in hrs. 15.0% 6.6%

% Wgt. Gain in 50 hrs. 29.0% 13.2%

% Wgt. Gain in 75 hrs. 37.5% 18.9%

it Wgt. Gain in 100 hrs. 43.1% 23.6%

Upon completion of the water pickup test the desiccant product, in itssame container, was heated to a temperature of 220 C. for 1 hour, cooledand weighted. The water the desiccant had taken up under test wasreleased and the initial 10 grams of product was found present in thedish. The dish and contents were re-exposed to the 39% H aqueoussolution of sulfuric acid for a second series of water pickup tests, the

results of which were in close agreement with those previously obtainedshowing that the product could be hydrated, dehydrated, and rehydratedand thus serve as a better desiccant than best quality commercialgranular P 0 It is essential to use the amorphous form of silica in thisprocess in order to obtain the orthosilicic acid intermediate compound.All of the following listed grades, classes, and

types of amorphous silica under various name designations have beenfound suitable for use: infusorial earth, siliceous or diatomaceousearth, kieselguhr, fossil flour, Dicalite," Kenite, Multicel, hydratedsilica and silicic acid (H SiO hydrated silicic acid with adsorbed water(H SiO -nH O with n l to 30 mols), and orthosilicic acid (H SiO preparedby reacting orthosilicate salts with mineral acids).

Solutions of pure orthophosphoric acid having 1-1 PO concentrationsranging from as little as 1% H PO to have been used in this processprovided sufficient water to meet stoichiometric requirements was alsopresent as such or in the hydrated silica ingredients when same wereused. Aqueous solutions of impure orthophosphoric acid could be employedwhere such impurities were determined to be predominantly metaandpyrophosphoric acids. lmpure acids containing as much as 4%pyrophosphoric acid (11 F 0 12% metaphosphoric acid (HPO and 34%orthophosphoric acid (P1 1 0 to give a content of 53% of equivalent H POused stoichiometrically based on their H PO equivalents produced highlysatisfactory products meeting both quality and quantity requirements forproduct manufacture.

The relative proportions of amorphous silica to orthophosphoric acidalone or in combination with either or both pyroand metaphosphoric acidscan be varied over wide ranges, and since the resulting mixtures can besubjected to any one or to all of four rather well defined temperatureranges to form compounds similar to those illustrated in equations 2 and6a.; 3 and 7, 4, 4a. and 8, and 5 and 9 it can be readily appreciatedthat the use of the process permits the preparation of a nearlyunlimited number of chemical compounds.

In general, when the ratio of H PO,:SiO exceeds approximately 8:1 theremoval of all of the water of constitution of the H PO becomes moredifficult and products heated to temperatures approaching 300 C. arevery hygroscopic and tend to remain as sticky, pasty solids; when heatedto temperatures approaching 500 C. they become less hygroscopic but aresticky, solid substances; when heated to 800 C. with loss of HPO theybecome non-hygroscopic or nearly so and are no longer sticky but becomeglassy, granular solids. Conversely, with increase of SiO :1-l PO ratio(for example, from 1:1 to 2:1) the removal of the water of constitutionoccurs very rapidly resulting in powdery products which are relativelynon-hygroscopic. In general, the water solubilities of the productsincrease with increasing ratios of H PO :SiO (for example, from 4:1 to6:1) and decrease with increasing ratios of SiO :H O (for example, from1:1 to 2:1 Likewise, product solubility in alcohols and in oxygenatedorganic compounds increases with increasing ratios of H PO :Si0 and alsowith products prepared at lowest temperatures (300 C.).

Products prepared either with H PO :SiO ratios greater than 8:1 andheated up to temperatures of 500 C., or products prepared with H PO:SiO- ratios greater than 1:1 and heated to 300 C. temperature exhibitthe highest levels of hygroscopicity. Products having 1-1 PO4SiO ratiosbetween 2:1 and 6:1 exhibit water pickup capacities greater than 40parts by weight of water pickup per 100 parts by weight of product per100 hours of time exposure to aqueous solutions of sulfuric acid (39%11:50,). The equivalent P 0 contents of the products increase both withincrease of H PO :SiO ratios and with increase of heating up totemperatures of approximately 550 C., while the equivalent P content isnearly the same percentagewise for all products having ratios of H PO:SiO between 2:1 and 8:1 which have been heated to temperatures ofapproximately 800 C.

The following table will serve to illustrate relationships betweenvarious ratios of H PO :SiO employed in the process, the amounts ofequivalents of 100% P1 1 0 used in the forms of aqueous solutions oforthophosphoric acid, the weights of products obtained at the differenttemperatures used, the percentages of P 0 of the products obtained, andthe P 0 input and recovery relationships.

CHARACTERIZATION OF PIJKXPERIMENTAL PRODUCTS PREPARED WITH dissolvedsubstances, for example, the pH values of aqueous solutions containing0.5 gram of complexes having empirical formulas H SiO HP0 and H SiO 'P O'4HPO in volumes of 100 c.c. of water were pH 1.6 and pH 1.8respectively.

If it is desired to use the process primarily to produce metaphosphoricacid (HPO solutions in which the ratio of orthophosphoric acid toamorphous silica is preferably greater than 7H PO :SiO are first heatedto the 500 C. temperature, then are heated to the 800 C. temperature toeffect volatilization of the HPO The residue after being freed of itscontent of volatilizable HPO can be reprocessed as a startingsilicacontent raw material with more orthophosphoric acid solution,heated to remove uncombined water and water of con- ATIOS OF HaPOuSiOzCONTENTS M01. ratios of H3P04ZS102 2:1 4:1 Aqueous acid solution usedexp. in grams of 100% H3PO4. 81. 8 98.0 Silica, 100% SiO; in grams 25.015.0 Product A, in grams from heating mix to 300 C. ternp 98. 8 99.0Percent eq. P205111 Product A 59. 7 71. 2 Product B, in grams fromheating Product A to 500 C. temp. 91. 3 90. 1 Percent eq. P205111Product B 64. 5 78. 1 Product C, in grams from heating Product B to 800C. ternp. 84.2 50. 5 Percent eq. P105 in Product 0 62.8 70.9 HPO;volatilized from Product B, in grams 6.8 39. 0 Sublimate of P1O tromheating Product C to 1,000 C. in grams. 52. 7 35. 7 Residue of S101obtained from heating Product C to 1,000 C.

temperature, in grams 24. 8 14. 8 Total P 0 equivalents in gramsintroduced as raw material 59.0 71.0 Eq. P of HPO; volatilized fromProduct B, in grams 6.0 34. 6 Eq. P105 lost in process, in grams 0. 30.7

VARIED atmospheric pressure. Hearing was by both natura gas andelectricity.

It is to be noted that the application of the process in the mannerdescribed below will provide for the preparation of optimum amounts ofproducts of desired composition.

1. Dry, granular products most suitable for use as heatregeneratabledesiccants and as dehydration reagents are prepared by heating mixturesof orthophosphoric acid and amorphous silica in ratios between 2HPO,,:SiO to 6H PO :SiO to temperatures in the range of 275 and 295 C.

2. Dry, granular products most suitable for use as source materials ofmetaphosphoric acid and phosphate phosphorus in water soluble andhydrolyzable form such as for use in high adult/51a? P10 contentagricultural chemicals are prepared by heating mixtures oforthophosphoric acid and amorphous silica in ratios between 6H PO :SiOto 8H PO :SiO- to tem peratures in the range of 475 to 525 C.

3. Dry, granular products most suitable for use as source materials forthe production of metaphosphoric acid (HPO are prepared by heatingmixtures of orthophosphoric acid and amorphous silica in ratios greaterthan 4H PO :SiO to temperatures in the range of 475 to 500 C. afterwhich the resultant products are further heated to temperatures abovestitution, and heated to the 800 C. temperature. This process can berepeated as often as may be desired. The present inven- 5 tion alsocomprises a unique process for the preparation of 600 C. up to 800 C. toliberate volatilized metaphosphoric acid.

4. Dry, granular products most suitable for preparing sublimed P 0 areprepared by heating mixtures of orthophosphoric acid and amorphoussilica of a ratio of 2H PO4:SiO2 to an initial temperature of about 500C. for the removal of uncombined water and of water of constitution,then heating the water-free residues to temperatures ranging between 885and 1,000 C. to effect sublimation of P 0 5. Dry, granular products mostsuitable for use as source materials of strongly ionizable hydrogen ionswhich allow such products to display strongly acidic characteristics inaddition to their possessing very strong dehydration capacities preparedby heating mixtures of orthophosphoric acid and amorphous silica inratios preferably between 2H PO :SiO

and 6H PO.,:SiO to either 300 C. temperature to obtain for of aqueoussolutions containing very small quantities of such pure metaphosphoricacid, heretofore obtained only by decomposition of metaphosphate saltspreferably at tempera tures below 0 by mineral acid decompositionreactions. Also, in the customary manner of dehydration of freeorthophosphoric acids by the use of heat, mixtures of products of theseveral stages of dehydration are always obtained and at temperaturesabove 300 C. a combination of volatilized metaphosphoric acid andsublimed phosphorus pentoxide are liberated. In the process of thepresent invention neither metaphosphoric acid or phosphorus pentoxideare liberated until red-heat temperatures (585-950 C.) are reached. Inthe present process the silicon pyrophosphate (SiP O produced by priorheating of the heteropoly acid complexes to 800 C. temperature yieldsthe amorphous form of P 0 when the silicon pyrophosphate is heated totemperatures in the range of red-heat, about 850 to 1,000 C. whichtemperatures are far below those of white heat, and yet considerablyabove the temperature of 250 C., the sublimation temperature of theamorphous form of P 0 As conventionally prepared, metaphosphoric acidalone is either syrupy and hygroscopic or is glassy and very sparinglysoluble in water with many isomeric forms being possible where thenumber of different metaphosphoric acids possible is due not only to thenumber of metaphosphoric acid molecules contained in them, but also asaffected by their internal arrangement. in the process of this inventionthe physical and chemical natures of the metaphosphoric acid can becontrolled such as to produce solid rather than liquid (syrupy) productshaving predetermined capacities for water adsorption and for watersolubilities by first forming the heteropoly acid complex compounds ofmetaphosphoric acid predominantly.

The following example further illustrates the use of the four previouslynoted temperature ranges in producing predetermined amounts of any oneor all of the products possible from processing a mixture of aqueousorthophosphoric acid solution and amorphous silica of a ratio of4l-l;,PO,,:SiO as described below.

A mixture of 23 grams of diatomaceous earth (97.45% SiO and 225 grams ofaqueous orthophosphoric acid solution composed of 65% l-l lO and 35percent water (such solution containing the equivalent of 105.9 grams ofP was heated to a temperature of 292 C. to produce 149.8 grams of a dry,solid product designated as product A, shown by chemical analysis tocontain the equivalent of 70.7% P 0 (equal to 105.9 grams of P 0 149.8grams of product A (from above) were further heated to a temperature of500 C. and 134.2 grams of a dry, solid product was recovered, designatedas product B, shown by chemical analysis to contain the equivalent of78.7% P 0 (equal to 105.6 grams of P 0 134.2 grams of product B (fromabove) were further heated to a temperature of 790 C. producing 88.5grams of a dry, solid product designated product C and 48.1 grams ofvolatilized metaphosphoric acid (HPO Chemical analysis showed product Cto contain the equivalent of 70.9% P 0 (equal to 62.7 grams P 0 and thevolatilized HPO to contain the equivalent of 88.7% P 0 (equal to 42.6grams of P 0 88.5 grams of product C (from above) were heated to atemperature of 960 C. producing 62.4 grams of a sublimate of 100% P 0content and a residue of 25.9 grams of crystalline silica (SiO Havingnow described preferred embodiments of my invention, it is not intendedthat it be limited, except as may be required by the appended claims.

What is claimed as new is as follows:

1. A process for the production and recovery of oxygencontainingcompounds of phosphorus or silicon from starting materials comprisingorthophosphoric acid and amorphous silica or its hydrates comprisingadding siliceous material selected from the group consisting ofamorphous silica, metasilicic acid, disilicic acid, and orthosilicicacid to an aqueous solution of orthophosphoric acid and thereafterheating at a temperature below 300 F. to dissolve the added silica andthen to effect volatilization and boiling off of at least some of thewater of solution and combined water of hydration and continuing saidheating to obtain dry solid heteropoly complex acid compounds of theformula l-l SiO 'XHPO where X is less than about 8.

2. The process of claim 1, including, in addition, steps of heating theheteropoly complex acid to a temperature between 300 and 575 C. andthereby obtaining a product represented by the general formula H SiO 'XPO -Yl-lOl where X and Y are each below 10.

3. The process of claim 2, including an additional heating step in whichthe product is decomposed to release HPO as a volatile product and SiPO, as a solid product and separately recovering said HPO; and said SiPO-,.

4. The process of claim 3 which comprises, in addition, heating said SiPO-, to between 575 and 800 C. add recovering the P 0 sublimed from saidSiP O 5. The process of claim 1 wherein the silica starting material isa solid amorphous SiO 6. The process of claim 1 wherein the silicastarting material is metasilicic acid.

7. A process for the production and recovery of oxygen containingcompounds of phosphorous or silicon which comprises the steps of:

a. adding a siliceous material selected from the group consisting ofamorphous silica, metasilicic acid, disilicic acid and orthosilicic acidto a solution of orthophosphoric acid;

b. heating the resulting product to a temperature below about 300 C. todissolve said added material and forming solid heteropoly acidcomplexes;

c. subsequently heating the solution obtained in (b) to a temperature ofbetween about 300-575 C. to effect condensation and to form otherheteropoly acid complexes with P 0 adducts;

d. further heating at a temperature of about 575-800 C. to releasevolatile metaphosphoric acid and leave a residue of siliconpyrophosphate;

e. heating at a temperature of about 8001,000 C. to decompose saidsilicon pyrophosphate to form phosphorous pentoxide and silicon dioxide.

8. The process of claim 7 wherein the relative proportions oforthophosphoric acid and siliceous material are between 2:1 and 8:1.

9. The process of claim 7 wherein said solid heteropoly complex acid hasthe formula H SiO 'XHPO where X is less than about 8.

10. The process of claim 7 wherein said other heteropoly acid complexwith P 0 adduct is represented by the general formula H SiO 'XP Or, YHPOYHPO wherein X and Y are each below 10.

11. The process of claim 7 wherein said HPO and said SiP O are recoveredseparately.

12. The process of claim 7 wherein the silica starting material is asolid amorphous SiO 13. The process of claim 7 wherein the silicastarting material is metasilicic acid.

14. A process for the production and recovery of oxygencontainingcompounds of phosphorus or silicon from orthophosphoric acid andamorphous silica or its hydrates as starting materials which comprisesmixing siliceous material selected from the group consisting ofamorphous silica, metasilicic acid, disilicic acid and orthosilicic acidin an aqueous solution of orthophosphoric acid in a mol ratio of H PO tosiliceous material of 2:1 to 8:1 and thereafter heating the resultingmixture to produce intermediate heteropoly complex acid compounds whichupon further heating within selected temperature ranges between about275 C. to about 1,000 C. are capable of producing specifiedoxygen-containing compounds of phosphorus and silicon.

15. A process according to claim 14 wherein said mol ratio is 2:1-6:1and said intermediate compounds are heated at 275-295 C. to produce adry, granular product suitable for use as heat-regeneratable desiccantand dehydrating agent.

16. A process according to claim 14 wherein said mol ratio is 6:1 to 8:1and said intermediate heteropoly complex acid compounds are heated to475-525 C. to produce a product suitable as a source for metaphosphoricacid and phosphate phosphorous in water soluble and hydrolyzable form.

17. A process according to claim 14 wherein said mol ratio is 4:1 to8:1, and said intermediate heteropoly complex acid compounds are firstheated to 475-500 C. and the resultant products thereafter furtherheated to 600 to 800 C. to liberate volatilized metaphosphoric acid.

18. A process according to claim 14 wherein said mol ratio is about 2:1,and said intermediate heteropoly complex acid compounds are first heatedto about 500 C. to remove all water and thereafter further heating to885 to l,000 C. to effect sublimation of P 0 19. A process according toclaim 14 wherein said mol ratio is 2:1 to 6:1 and said mixture is heatedto either 300 or 500 C. to obtain a heteropoly acid complex of stronglyacidic character and possessing strong dehydration capacity.

20. Dry, granularproducts suitable for use as heatregeneratabledesiccants and as dehydration reagents prepared in accordance with theprocess of claim 15.

21. Dry granular products suitable for use as source materials ofmetaphosphoric acid and phosphate phosphorus in water soluble andhydrolyzable form such as for use in high equivalent P 0 contentagricultural chemicals prepared in accordance with the process of claim23.

22. Dry, granular products suitable for use as source materials for theproduction of metaphosphoric acid prepared in accordance with theprocess of claim 24.

23. Dry, granular products suitable for preparing sublimed P 0 preparedin accordance with the process of claim 18.

24. Dry, granular products suitable for use as source materiwith theprocess of claim 19.

=1 v l l

2. The process of claim 1, including, in addition, steps of heating theheteropoly complex acid to a temperature between 300* and 575* C. andthereby obtaining a product represented by the general formulaH2SiO3.XP2O5.YHOP3 wherein X and Y are each below
 10. 3. The process ofclaim 2 including an additional heating step in which the product isdecomposed to release HPO3 as a volatile product and SiP2O7 as a solidproduct and separately recovering said HPO3 and said SiP2O7.
 4. Theprocess of claim 3 which comprises, in addition, heating said SiP2O7 tobetween 575* and 800* C. and recovering the P2O5 sublimed from saidSiP2O7.
 5. The process of claim 1 wherein the silica starting materialis a solid amorphous SiO2.
 6. The process of claim 1 wherein the silicastarting material is metasilicic acid.
 7. A process for the productionand recovery of oxygen containing compounds of phosphorous or siliconwhich comprises the steps of: a. adding a siliceous material selectedfrom the group consisting of amorphous silica, metasilicic acid,disilicic acid and orthosilicic acid to a solution of orthophosphoricacid; b. heating the resulting product to a temperature below about 300*C. to dissolve said added material and forming solid heteropoly acidcomplexes; c. subsequently heating the solution obtained in (b) to atemperature of between about 300*-575* C. to effect condensation and toform other heteropoly acid complexes with P2O5 adducts; d. furtherheating at a temperature of about 575*-800* C. to release volatilemetaphosphoric acid and leave a residue of silicon pyrophosphate; e.heating at a temperature of about 800*-1,000* C. to decompose saidsilicon pyrophosphate to form phosphorous pentoxide and silicon dioxide.8. The process of claim 7 wherein the relative proportions oforthophosphoric acid and siliceous material are between 2:1 and 8:1. 9.The process of claim 7 wherein said solid heteropoly complex acid hasthe formula H2SiO3.XHPO3 where X is less than about
 8. 10. The processof claim 7 wherein said other heteropoly acid complex with P2O5 adductis represented by the general formula H2SiO3.XP2O5.YHPO3 wherein X and Yare each below
 10. 11. The process of claim 7 wherein said HPO3 and saidSiP2O7 are recovered separately.
 12. The process of claim 7 wherein thesilica starting material is a solid amorphous SiO2.
 13. The process ofclaim 7 wherein the silica starting material is metasilicic acid.
 14. Aprocess for the production and recovery of oxygen-containing compoundsof phosphorus or silicon from orthophosphoric acid and amorphous silicaor its hydrates as starting materials which comprises mixing siliceousmaterial selected from the group consisting of amorphous silica,metasilicic acid, disilicic acid and orthosilicic acid in an aqueoussolution of orthophosphoric acid in a mol ratio of H3PO4 to siliceousmaterial of 2:1 to 8:1 and thereafter heating the resulting mixture toproduce intermediate heteropoly complex acid compounds which uponfurther heating within selected temperature ranges between about 275* C.to about 1,000* C. are capable of producing specified oxygen-containingcompounds of phosphorus and silicon.
 15. A process according to claim 14wherein said mol ratio is 2: 1-6:1 and said intermediate compounds areheated at 275*-295* C. to produce a dry, granular product suitable foruse as heat-regeneratable desiccant and dehydrating agent.
 16. A processaccording to claim 14 wherein said mol ratio is 6: 1 to 8:1 and saidintermediate heteropoly complex acid compounds are heated to 475*-525*C. to produce a product suitable as a source for metaphosphoric acid andphosphate phosphorous in water soluble and hydrolyzable form.
 17. Aprocess according to claim 14 wherein said mol ratio is 4: 1 to 8:1, andsaid intermediate heteropoly complex acid compounds are first heated to475*-500* C. and the resultant products thereafter further heated to600* to 800* C. to liberate volatilized metaphosphoric acid.
 18. Aprocess according to claim 14 wherein said mol ratio is about 2:1, andsaid intermediate heteropoly complex acid compounds are first heated toabout 500* C. to remove all waTer and thereafter further heating to 885*to 1,000* C. to effect sublimation of P2O5.
 19. A process according toclaim 14 wherein said mol ratio is 2: 1 to 6:1 and said mixture isheated to either 300* or 500* C. to obtain a heteropoly acid complex ofstrongly acidic character and possessing strong dehydration capacity.20. Dry, granular products suitable for use as heat-regeneratabledesiccants and as dehydration reagents prepared in accordance with theprocess of claim
 15. 21. Dry, granular products suitable for use assource materials of metaphosphoric acid and phosphate phosphorus inwater soluble and hydrolyzable form such as for use in high equivalentP2O5 content agricultural chemicals prepared in accordance with theprocess of claim
 23. 22. Dry, granular products suitable for use assource materials for the production of metaphosphoric acid prepared inaccordance with the process of claim
 24. 23. Dry, granular productssuitable for preparing sublimed P2O5 prepared in accordance with theprocess of claim
 18. 24. Dry,036524023 granular products suitable foruse as source materials of strongly ionizable hydrogen ions prepared inaccordance with the process of claim 19.